The pot plant Kalanchoë seems to suffer less from aphids and Phytophthora when grown in a mix containing compost. This is evident from research by Wageningen University & Research BU Greenhouse Horticulture. The substrate on which the Kalanchoë grew contained 10% spent mushroom substrate or 15% compost, reducing the need for peat. Researcher Esmée de Graaf: "The plants became more resilient against both above-ground pest and belowground disease with the addition of compost."
Kalanchoës are small, colorful potted plants that typically grow in a potting mix partially composed of peat. The horticulture sector has committed to increasing the use of sustainable components in potting soil mixtures, necessitating the search for alternatives to for example peat. Current potting soil mixtures contain peat. Composted plant material is one of the options to increase part of the potting soil mixtures. The spent mushroom substrate is a waste product from mushroom cultivation. The quality of compost must be sufficient to support healthy plant growth, and ideally, it should even improve cultivation outcomes.
In Kalanchoë cultivation, the oomycete Phytophthora can cause problems belowground by causing plants to wilt, while above-ground, aphids pose challenges. WUR studied whether the use of compost or spent mushroom substrate could mitigate these issues at its research facility in Bleiswijk. This was indeed the case. De Graaf: "The addition of compost resulted in fewer disease symptoms and a reduced aphid reproduction rate. This is likely due to a different microbiome composition."
WUR examined various types of components, including regular green compost and spent mushroom substrate. In the study, the potting soil contained 15% green compost; for the spent mushroom substrate, the proportion was slightly lower due to its high salt content. "In January 2025, we will repeat the trial to confirm the results. In new research starting in 2025, WUR aims to develop indicators for resilient composts."
Within the project 'Above and below-ground resilience steering,' research is also being conducted on chrysanthemums, cucumbers, and Kalanchoë. This research is a public-private partnership (PPS) involving Topsector Tuinbouw & Uitgangsmaterialen, Wageningen University & Research BU Glastuinbouw, Glastuinbouw Nederland, Stichting Kennis in je Kas (KijK), Telersverenigingen Komkommer, Chrysant en Gerbera, Cercam B.V., and Innovatiefonds HagelUnie.